JP6728829B2 - Electronic control unit - Google Patents

Description

The present invention relates to an electronic control device that controls an internal combustion engine mounted on a vehicle.

Urea SCR system using a selective catalytic reduction (hereinafter abbreviated as SCR) catalyst and a urea water injector as a technology for removing nitrogen oxides (hereinafter referred to as NOx) in exhaust gas discharged from a vehicle engine. It has been known. In the urea SCR system, the SCR catalyst and the urea water injector are installed in the exhaust pipe, and the urea water injector injects an amount of urea water necessary for reducing NOx in the SCR catalyst into the exhaust pipe.

In European On-Board Diagnostics (hereinafter abbreviated as EOBD), the "EOBD EURO6" regulation for large vehicles is a reducing agent for vehicles that do not have a function to heat the reducing agent (hereinafter also referred to as a vehicle without a heating system). Is frozen, the fail-safe process is started when the freezing continues for 70 minutes while the engine is operating. Note that, hereinafter, the processing performed when such a reducing agent is frozen is also referred to as a reducing agent freeze monitoring logic.

However, according to the regulation described above, a vehicle having a function of heating the reducing agent (hereinafter, also referred to as a vehicle equipped with a heating system) does not need to execute the reducing agent freeze monitoring logic. In addition, the vehicle equipped with the heating system is a vehicle that is recognized that the reducing agent is thawed within 70 minutes even if the reducing agent is frozen at -7°C or lower at the time of authentication.

JP, 2005-001282, A

In a vehicle equipped with a heating system, if the heating system fails, the following problems occur. That is, in a vehicle equipped with a heating system having a failure in the heating system, even if the reducing agent freezes at -7°C or lower, the frozen reducing agent cannot be heated. Therefore, the reducing agent remains frozen and the urea water cannot be injected, and there is a concern that the environment will deteriorate. In addition, even if the reducing agent cannot be heated in this way, the reducing agent freeze monitoring logic is not executed because the vehicle is equipped with a heating system, and as a result, failsafe processing is not performed. It is not possible to even call the user's attention such as turning on a warning lamp.

The present invention has been made in view of the above circumstances, and an object thereof is to cause a situation in which a fail-safe process is not executed in a vehicle equipped with a heating system even though the reducing agent is frozen for a long time. An object of the present invention is to provide an electronic control device capable of suppressing the above.

The electronic control device according to the first aspect includes a freeze detection unit (31), a failure determination unit (32), and a fail-safe determination unit (33). The freezing detection unit detects freezing of the reducing agent injected into the exhaust gas in order to purify the exhaust gas discharged from the internal combustion engine (2) mounted on the vehicle. The failure determination unit determines whether the heating system (20) for heating the frozen reducing agent is normal. The fail-safe determination unit determines whether to execute a fail-safe process corresponding to the freezing of the reducing agent, based on the detection result of the freezing detection unit and the determination result of the failure determination unit. In addition, the fail-safe determination unit executes a fail-safe process when it determines that the reducing agent is not frozen by the time when a predetermined determination time elapses from the time when the reducing agent is frozen, and the failure determination unit causes the heating system to operate. The determination time is shortened according to the period when it is determined that is not normal.

According to such a configuration, it is possible to execute the same processing as the above-described reducing agent freezing monitoring logic in consideration of the failure state of the heating system in addition to the frozen state of the reducing agent. Therefore, according to the present means, it is possible to suppress the occurrence of the situation in which the fail-safe process is not executed in the vehicle equipped with the heating system, even though the reducing agent is frozen for a long time.

The figure which shows typically the structure of ECU and its peripheral device which concern on 1st Embodiment. The figure which shows the function which the post-processing ECU has typically Flowchart showing the contents of the FS necessity determination process Timing chart that schematically shows the state of each part 1 Timing chart that schematically shows the state of each part 2 Timing chart that schematically shows the state of each part 3 Timing chart that schematically shows the state of each part 4 Flowchart showing the flow of FS necessity determination processing according to the second embodiment Timing chart that schematically shows the state of each part 5 The flowchart which shows the content of the FS necessity determination process which concerns on 3rd Embodiment. Timing chart that schematically shows the state of each part 6 The flowchart which shows the content of the FS necessity determination process which concerns on 3rd Embodiment. Timing chart that schematically shows the state of each part 7 Timing chart that schematically shows the state of each part 8 Timing chart that schematically shows the state of each part 9 The figure which shows typically the structure of ECU and its peripheral device which concern on other embodiment. The figure which shows typically the function which a post-processing integrated engine ECU has.

Hereinafter, a plurality of embodiments of the present invention will be described with reference to the drawings. In addition, in each embodiment, the substantially same configurations are denoted by the same reference numerals, and description thereof will be omitted.
(First embodiment)
Hereinafter, the first embodiment of the present invention will be described with reference to FIGS.

As shown in FIG. 1, an engine ECU 1 is mounted on a vehicle and controls a diesel engine 2 (hereinafter, also referred to as engine 2) corresponding to an internal combustion engine. The internal combustion engine is not limited to the diesel engine, but may be, for example, a gasoline engine. The engine 2 is provided with an injector 3 that injects fuel into the corresponding cylinder for each of the plurality of cylinders. Note that FIG. 1 shows only the injector 3 corresponding to one cylinder.

To the injector 3, a fuel supply pipe 5 extending from a common rail 4 which is a fuel pressure accumulator is connected. Fuel stored in a fuel tank 6 of the vehicle is pumped to the common rail 4 by a fuel pump 8 via a pipe 7. As a result, the high-pressure fuel stored in the common rail 4 is supplied to the injector 3 via the fuel supply pipe 5. The engine ECU 1 drives the injector 3 to control fuel injection into the engine 2.

The engine ECU 1 is mainly composed of a microcomputer including a CPU, ROM, RAM and the like (not shown). Signals output from an accelerator opening sensor, a rotation speed sensor, and the like (not shown) are given to the engine ECU 1. Further, the engine ECU 1 is provided with a signal output from a fuel pressure sensor 9 that detects the fuel pressure accumulated in the common rail 4.

The engine ECU 1 executes injection pressure control for controlling the fuel pressure accumulated in the common rail 4. In the injection pressure control, the operating state of the engine 2 is detected from the accelerator opening degree and the rotation speed, and a target rail pressure suitable for the operating state is set. Then, the discharge amount of the fuel pump 8 is feedback-controlled so that the rail pressure detected by the fuel pressure sensor 9 matches the target rail pressure.

The engine ECU 1 executes fuel injection control that controls the fuel injection amount and injection timing of the injector 3. In the fuel injection control, the optimum injection amount and injection timing according to the operating state of the engine 2 are calculated based on the engine speed, the accelerator opening degree, the rail pressure, etc., and the fuel injection of the injector 3 is performed according to the calculation result. Controlled. The engine ECU 1 performs data communication with the post-processing ECU 11 mounted on the vehicle via the communication bus 10. The post-processing ECU 11 controls the exhaust gas purification device 12 that purifies the exhaust gas discharged from the engine 2.

The exhaust gas purification device 12 includes an SCR catalyst 13, a urea water injector 14, a urea water tank 15, a urea water pump 16, a pipe 17, a NOx sensor 18, a pressure sensor 19, a heating system 20, and the like. The SCR catalyst 13 as a reduction catalyst and the urea water injector 14 are provided in an exhaust pipe 21 that constitutes a passage for exhaust gas discharged from the engine 2. The urea water injector 14 injects urea water, which is a reducing agent, into the exhaust pipe 21. The urea water injected from the urea water injector 14 is mixed with the exhaust gas and then flows into the SCR catalyst 13.

Urea water is stored in the urea water tank 15. The urea water stored in the urea water tank 15 is pressure-fed by the urea water pump 16 and supplied to the urea water injector 14 via the pipe 17. The NOx sensor 18 is provided in the exhaust pipe 21 on the path from the SCR catalyst 13 to the outside of the vehicle, and detects the NOx concentration of the exhaust. The pressure sensor 19 is provided in the urea water pump 16 and detects the pressure for pumping the urea water.

The post-processing ECU 11 is mainly composed of a microcomputer including a CPU, a ROM, a RAM and the like (not shown). The post-treatment ECU 11 calculates the urea water amount based on the NOx concentration detected by the NOx sensor 18 so that the NOx contained in the exhaust gas can be removed by the reduction reaction of the SCR catalyst 13. The post-processing ECU 11 controls the injection amount of urea water by driving the urea water injector 14 based on the calculated urea water amount. The post-processing ECU 11 performs data communication with the engine ECU 1 via the communication bus 10.

As shown in FIG. 2, the post-processing ECU 11 has functions as a freeze detection unit 31, a failure determination unit 32, and a fail-safe determination unit 33. The freezing detection unit 31 determines whether or not the pressure of the urea water pump 16 has appropriately changed according to the injection amount command, based on the detection result of the pressure sensor 19. The freeze detection unit 31 determines that the urea water is frozen when the pressure of the urea water pump 16 does not appropriately change according to the injection amount command. That is, the freezing detection unit 31 detects the freezing of the reducing agent.

The heating system 20 is for heating the frozen urea water, and is composed of an electric heater or the like attached to the urea water tank 15 in the present embodiment. Although not shown, the electric heater forming the heating system 20 may be attached to the pipe 17. Further, the heating system 20 is not limited to the configuration in which the electric heater is provided, and a configuration in which the urea water is heated using the heat generated from the motor in accordance with the operation of the urea water pump 16 may be adopted.

The operation of the heating system 20 is controlled by the post-processing ECU 11. Specifically, when the post-treatment ECU 11 detects freezing of the urea water, the post-processing ECU 11 causes the heating system 20 to generate heat to melt the urea water. After the heating system 20 starts the heat generation operation, the post-processing ECU 11 determines that the urea water has been thawed and then stops the heat generation operation by the heating system 20 when freezing of the urea water is no longer detected.

A temperature sensor (not shown) is attached near the heating system 20. The failure determination unit 32 determines, based on the detection result of the temperature sensor, whether or not the heating operation by the heating system 20 is normally executed. That is, the failure determination unit 32 determines whether the heating system 20 is normal.

The fail-safe determination unit 33 determines, based on the detection result of the freezing detection unit 31 and the determination result of the failure determination unit 32, whether or not to execute the fail-safe process corresponding to the freezing of the urea water that is the reducing agent. The necessity determination process is executed. The post-processing ECU 11 transmits the execution result of the FS necessity determination processing, that is, information such as the determination result of whether or not to execute the fail-safe processing, to the engine ECU 1 via the communication bus 10. The engine ECU 1 controls the execution of the fail-safe processing corresponding to the freezing of the urea water that is the reducing agent, based on various information transmitted from the post-processing ECU 11.

Examples of fail-safe processing include "Warning", "Low Level Induction Operation", and "Severe Level Induction Operation". In “Warning”, for example, a lamp or the like provided on the instrument panel for urging the user to warn is turned on. In the "Low Level Induction operation", for example, a torque limit of 75% is implemented. In the "Severe Level Induction operation", for example, the traveling speed of the vehicle is limited to a preset low speed (for example, 20 km/h) or less. However, the fail-safe processing that is executed by the engine ECU 1 to cope with the freezing of the reducing agent is either "Warning" or "Severe Level Induction Operation". In the following, "Severe Level Induction operation" is simply abbreviated as "Severe".

Next, the operation of the above configuration will be described.
In the following description, urea water that is a reducing agent will be simply referred to as a reducing agent. In the FS necessity determination process executed by the post-processing ECU 11, it is determined whether the fail-safe process is performed based on the detection result of the reducing agent freezing and the determination result of whether the heating system 20 is normal. Specifically, in the present embodiment, if it is determined that the reducing agent is not frozen by the time when a predetermined determination time elapses from the time when the reducing agent is frozen, the fail-safe process of “Severe” is performed. It is decided to implement. Although the details will be described later, the determination time changes within a predetermined range depending on whether or not there is a failure in the heating system 20. Then, of the changing judgment times, the longest one is called the basic judgment time.

Although not shown, the post-processing ECU 11 includes a counter for measuring the period during which the reducing agent is frozen, that is, the freezing duration time of the reducing agent in the FS necessity determination process. The post-processing ECU 11 performs a first count-up operation of integrating the counter with the coefficient A, that is, incrementing by the coefficient A, and a second count-up operation of integrating the counter with the coefficient B, that is, incrementing by the coefficient B. Execute selectively. The first and second count-up operations end when the count value reaches a predetermined determination value.

It should be noted that the coefficient A is the basic determination time when the first count-up operation is started from the state where the count value is the initial value (for example, zero), from the start time to the time when the count value reaches the determination value. The value is set to be (for example, 70 minutes). Further, when the second count-up operation is started from the state where the count value is the initial value, the coefficient B is a time required from the start time to the time when the count value reaches the judgment value, which is shorter than the basic judgment time ( The value is set to be, for example, 20 minutes. That is, the relationship is "coefficient A<coefficient B". The determination value is appropriately set within the range where the coefficients A and B satisfy the above conditions.

Hereinafter, the flow of the FS necessity determination process will be described first with reference to the flowchart in FIG. 3, and then a specific determination example will be described with reference to the timing charts in FIGS. 4 to 7.

"Details of FS necessity determination process"
When the FS necessity determination process shown in FIG. 3 is started, it is first determined in step S110 whether or not the reducing agent is frozen. If freezing of the reducing agent is detected, "YES" is determined in the step S110 and the process proceeds to the step S120. In step S120, it is determined that the "Warning" fail-safe process is to be performed.

On the other hand, if freezing of the reducing agent is not detected, “NO” is determined in the step S110, and the process proceeds to the step S130. In step S130, the count value of the counter is cleared to an initial value of zero. That is, the engine ECU 1 clears the count value of the counter for measuring the freezing duration when the freezing of the reducing agent is not detected. After step S130, the process proceeds to step S140, and if some sort of fail-safe processing is executed, that processing is canceled.

In step S150 executed after step S120, it is determined whether or not the heating system 20 is normal. When it is determined that the heating system 20 is normal, “YES” is determined in the step S150, and the process proceeds to the step S160. In step S160, the first count-up operation is executed. On the other hand, when it is determined that the heating system 20 is not normal but has a failure, “NO” in the step S150 and the process proceeds to a step S170. In step S170, the second count-up operation is executed.

In other words, the post-processing ECU 11 executes the first count-up operation if it is determined that the heating system 20 is normal when the reducing agent is frozen, and the heating system 20 is not normal and fails. If it is determined that the second count up operation is performed, the second count up operation is executed. As a result, the counting operation in the failure period in which it is determined that the heating system 20 has failed is faster than the counting operation in the normal period in which the heating system 20 is determined to be normal. According to such processing, the determination time for determining whether or not the fail-safe processing can be performed is shortened according to the length of the failure period.

After execution of step S160 or S170, the process proceeds to step S180. In step S180, it is determined whether the count value has reached the determination value. If the count value has reached the determination value, "YES" is determined in the step S180 and the process proceeds to the step S190. In step S190, it is determined that the "Severe" fail-safe process is to be performed. On the other hand, if the count value has not reached the determination value, “NO” is determined in the step S180, the process returns to the step S110, and the processes after the step S110 are repeated. That is, the post-processing ECU 11 determines that the determination time has elapsed when the count value of the counter reaches the determination value without freezing the reducing agent, and determines that the “Severe” fail-safe process is performed.

"Specific example 1"
Here, as shown in FIG. 4, it is assumed that the heating system 20 is normal and the freezing of the reducing agent is eliminated by the time the determination time elapses after the reducing agent freezes. In this case, when freezing of the reducing agent is detected at time t1, the "Warning" fail-safe process is performed and the first count-up operation is started. Further, at this time, the post-processing ECU 11 starts the heat generation operation by the heating system 20.

As a result, the freezing of the reducing agent is canceled by the time the first count-up operation by the counter ends, that is, at time t2 before the count value reaches the determination value. Therefore, at time t2, the count value of the counter is cleared to the initial value, the execution of the "Warning" fail-safe process is canceled, and the normal state is restored. Further, at this time, the post-processing ECU 11 stops the heat generation operation by the heating system 20.

"Specific example 2"
Here, as shown in FIG. 5, although the heating system 20 is normal, until the judgment time elapses after the reducing agent freezes due to a failure, a defect or the like at a place different from the heating system 20. It is assumed that the freezing of the reducing agent will not be resolved. In this case, the operation at time t1 is the same as in “Specific example 1”. However, in this case, the freezing of the reducing agent is not eliminated when the first count-up operation by the counter is completed, that is, at time t2 when the count value reaches the determination value.

Therefore, at time t2, the fail-safe process of "Severe" is performed. Further, at this time, the post-processing ECU 11 stops the heat generation operation by the heating system 20. In this case, the time required from the detection of the freezing of the reducing agent to the execution of the "Severe" fail-safe processing is the basic determination time (for example, 70 minutes).

"Specific example 3"
Here, as shown in FIG. 6, it is assumed that the heating system 20 is out of order and the freezing of the reducing agent is not canceled by the time the determination time elapses after the reducing agent freezes. In this case, it is determined that the heating system 20 is out of order at time t0 before time t1 when the freezing of the reducing agent is detected. Therefore, at time t1, when the freezing of the reducing agent is detected, the fail-safe process of "Warning" is performed and the second count-up operation is started.

At this time, the heating system 20 is out of order and cannot generate heat. As a result, when the second count-up operation is completed, that is, at time t2 when the count value reaches the determination value, the freezing of the reducing agent is not eliminated. Therefore, at time t2, the fail-safe process of "Severe" is performed. In this case, the time required from the detection of the freezing of the reducing agent to the execution of the "Severe" fail-safe processing is the time in the specific example 2, that is, the time shorter than the basic determination time ( For example, 20 minutes).

"Specific example 4"
Here, as shown in FIG. 7, it is assumed that the heating system 20 fails during execution of the heat generation operation and the freezing of the reducing agent is not canceled by the time the determination time elapses after the reducing agent freezes. .. In this case, the operation at time t1 is the same as in “Specific example 1”. However, in this case, at time t2 after the heating system 20 starts the heat generation operation, the heating system 20 that was normal until then fails. Therefore, after the time t2, the operation of the counter is changed from the first count-up operation to the second count-up operation.

At this time, since the heating system 20 is out of order, the heating operation cannot be performed. As a result, when the second count-up operation is completed, that is, at time t3 when the count value reaches the determination value, the reducing agent is not frozen. Therefore, at time t3, the fail safe process of "Severe" is performed. In this case, the time required from the detection of the freezing of the reducing agent to the execution of the "Severe" fail-safe process is shorter than the basic determination time and longer than the time in the specific example 3 ( For example, 30 minutes).

According to this embodiment described above, the following effects can be obtained.
Since the configuration of the present embodiment includes the heating system 20 that heats the frozen reducing agent, it is applied to a vehicle equipped with the heating system. Then, the post-processing ECU 11 determines whether or not to execute the fail-safe process corresponding to the freezing of the reducing agent, in consideration of the failure state of the heating system 20 in addition to the freezing state of the reducing agent. Perform judgment processing. As a result, if the frozen state of the reducing agent cannot be resolved for a long time due to a failure of the heating system 20, a failure of a portion other than the heating system 20, a malfunction, etc., a “Severe” fail-safe process is performed. To be done. Therefore, according to the present embodiment, in the vehicle equipped with the heating system, the occurrence of a situation in which the fail-safe process is not executed despite the frozen state of the reducing agent continues for a long time is suppressed. That is, according to the present embodiment, it is possible to prevent the occurrence of a situation in which the environment is deteriorated by the vehicle traveling normally while the reducing agent is frozen.

Even if the reducing agent freezes, if the heating system 20 is normal, there is a high possibility that the frozen reducing agent will be melted within a predetermined time set by law. On the other hand, when the heating system 20 is out of order, the frozen reducing agent is unlikely to be melted within the predetermined time. In consideration of such a point, in the FS necessity determination process, the time from the detection of the freezing of the reducing agent to the execution of the fail-safe process is determined according to the length of the failure period in which the heating system 20 is out of order. That is, the determination time is shortened.

By doing so, it is possible to prevent the fail-safe process from being erroneously performed when the heating system 20 is normal and the reducing operation can be melted within the predetermined time set by the regulation due to the heat generation operation. It Further, when the heating system 20 is out of order and it is unlikely that the reducing agent can be melted within the above-mentioned predetermined time, fail-safe processing is promptly carried out, and as a result, the state in which the exhaust gas adversely affects the environment is promptly confirmed. Can be resolved.

In the present embodiment, if the heating system 20 fails in a state where the reducing agent is frozen, the fail-safe process is not immediately performed, and the fail-safe processing is performed after a lapse of a predetermined time after the failure of the heating system 20 is detected. Safe processing is implemented. The reason for doing this is as follows.

That is, when the reducing agent is frozen and the heating system 20 is out of order, it is unlikely that the exhaust gas cannot be purified, but the vehicle can be driven. Moreover, at this time, since the "Warning" fail-safe process has already been performed, the user is notified of the occurrence of the abnormality by a warning lamp or the like. In such a situation, if the "Severe" fail-safe process is immediately performed, that is, if the traveling speed is limited to a low speed, the user may feel uneasy. Further, when the user voluntarily attempts the evacuation traveling such as stopping the vehicle on the shoulder of the road in response to the notification of the occurrence of the abnormality, the evacuation traveling may be hindered. Therefore, as described above, even after the failure of the heating system 20 is detected, by delaying the execution of the fail-safe processing for a predetermined time, it is possible to prevent the user from feeling anxious or hindering the evacuation traveling. You can

(Second embodiment)
The second embodiment will be described below with reference to FIGS. 8 and 9.
In the second embodiment, the processing content of the FS necessity determination processing is different from that in the first embodiment. Since the configuration is common to the first embodiment, it will be described with reference to FIG.

"Details of FS necessity determination process"
In the FS necessity determination process of the present embodiment shown in FIG. 8, if it is determined that the heating system 20 is out of order, that is, if “NO” in step S150, step S270 is executed. In step S270, the count value of the counter is forcibly set to the determination value. Therefore, in step S180 executed after step S270, it is determined that the count value has reached the determination value regardless of the progress of the counting operation up to that point, and the result is “YES”. Due to such a process change, in the present embodiment, when it is determined that the heating system 20 is out of order, it is immediately determined that the "Severe" fail-safe process needs to be performed.

"Specific example 5"
Here, similar to “Specific Example 4” in the first embodiment, it is assumed that the heating system 20 fails during the execution of the heating operation. In this case, as shown in FIG. 9, the operation at time t1 is the same as in “Specific example 4”. However, in this case, the operation at time t2 when it is determined that the heating system 20 has failed is different. That is, when it is determined that the heating system 20 has failed at time t2, the count value is forcibly set to the determination value. Therefore, at time t2, the fail-safe process of "Severe" is performed.

According to this embodiment described above, the following effects can be obtained.
If the reducing agent is frozen and the heating system 20 is out of order, it is unlikely that the exhaust gas cannot be purified. Therefore, in the present embodiment, if the heating system 20 fails in the state where the reducing agent is frozen, the "Severe" fail-safe process is immediately performed. By doing so, it is possible to shorten the period in which the vehicle normally runs in a state where the exhaust gas cannot be purified, and to more quickly eliminate the situation in which the exhaust gas adversely affects the environment.

(Third Embodiment)
Hereinafter, the third embodiment will be described with reference to FIGS. 10 and 11.
In the third embodiment, the processing content of the FS necessity determination processing is different from that in the first embodiment. Since the configuration is common to the first embodiment, it will be described with reference to FIG. However, in this case, the post-processing ECU 11 can execute the countdown operation of subtracting the counter by the coefficient C, that is, decrementing by the coefficient C in the FS necessity determination processing. The coefficient C has no relationship with the coefficients A and B and is set to a predetermined value.

"Details of FS necessity determination process"
In the FS necessity determination process of the present embodiment shown in FIG. 10, if freezing of the reducing agent is not detected, that is, if “NO” in step S110, step S331 is executed. In step S331, it is determined whether or not the count value of the counter is larger than the initial value of zero. Here, when the count value is the initial value, the result is “NO” in step S331, and the process proceeds to step S140 without executing step S332. On the other hand, when the count value is larger than the initial value, “YES” is determined in the step S331, and the process proceeds to the step S332.

In step S332, the countdown operation is executed. After step S332, the process proceeds to step S140. Due to such a change in the process, in the present embodiment, the count value is returned toward the initial value during the period when the heating system 20 is determined to be normal and the freezing of the reducing agent is not detected. A countdown operation corresponding to the count operation will be executed.

"Specific example 6"
Here, as shown in FIG. 11, it is assumed that the heating system 20 is normal and the reducing agent is frozen and then thawed and then frozen again. In this case, the operation at time t1 is the same as that in “Specific example 1” of the first embodiment. Then, also in this case, the freezing of the reducing agent is eliminated at time t2 before the count value reaches the determination value, as in “Specific Example 1”. However, in this case, the countdown operation is started at time t2.

Then, at time t3 before the count value of the counter reaches the initial value, freezing of the reducing agent is detected again. Therefore, at time t3, the first count-up operation is started. However, in this case, the first count-up operation is started from a value whose count value is larger than the initial value. After that, the freezing of the reducing agent is not eliminated even at the time t4 when the count value reaches the determination value due to a failure or a defect in a portion other than the heating system 20.

Therefore, at time t4, "Severe" fail-safe processing is performed. In this case, the time required from the detection of the freezing of the reducing agent again to the execution of the "Severe" fail-safe processing is shorter than the basic determination time (for example, 50 minutes).

According to this embodiment described above, the following effects can be obtained.
If the reducing agent is once frozen, even if it is thawed after that, it is highly likely to be frozen again because the temperature of the surrounding environment is low. In such a case, freezing and thawing of the reducing agent are repeated within a relatively short time. Therefore, if the count value is cleared when the freezing is resolved, the count value does not easily reach the determination value, and fail-safe processing is not performed.

Therefore, in the present embodiment, when the reducing agent is once frozen and then thawed, a countdown operation of returning the count value toward the initial value from the time point when it is detected that the freezing is resolved without clearing the count value To start. By doing this, if the reducing agent is once frozen and then thawed, and then re-frozen in a relatively short time, the fail-safe process will be performed when the frozen state continues for a time shorter than the basic determination time. Will be implemented.

(Fourth Embodiment)
Hereinafter, the fourth embodiment will be described with reference to FIGS.
In the fourth embodiment, the processing content of the FS necessity determination processing is different from that in the first embodiment. Since the configuration is common to the first embodiment, it will be described with reference to FIG. However, in this case, the post-processing ECU 11 performs only the first count-up operation in the FS necessity determination process, and sets the determination value to be compared with the count value to either the first set value or the second set value. It is supposed to switch.

The first set value is the same as the determination value in each of the above embodiments. On the other hand, for the second set value, when the first count-up operation is started from the state where the count value is the initial value, the time required from the start time to the time when the count value reaches the second set value is the basic determination time. The value is set to a shorter time (for example, 50 minutes). That is, there is a relationship of “first set value>second set value”.

"Flow of FS necessity determination process"
In the FS necessity determination process of the present embodiment shown in FIG. 12, when it is determined that the heating system 20 is normal, that is, when “YES” in step S150, step S461 is executed. In step S461, the determination value is set to the first set value. On the other hand, if it is determined that the heating system 20 is out of order, that is, if “NO” in the step S150, the step S462 is executed. In step S462, the determination value is set to the second set value.

After executing step S461 or S462, the process proceeds to step S463. In step S463, the first count-up operation is executed as in step S160. After the execution of step S463, the process proceeds to step S180, and it is determined whether or not the count value has reached the determination value set at that time.

"Specific example 7"
Here, as shown in FIG. 13, as in “Specific example 2” in the first embodiment, although the heating system 20 is normal, it is caused by a failure, a defect, etc. at a place different from the heating system 20. It is assumed that the freezing of the reducing agent is not canceled by the time the determination time elapses after the reducing agent freezes. In this case, the operation at time t1 is the same as in “Specific example 2”. Since the heating system 20 is normal, the determination value is fixed at the first set value. As a result, the count value reaches the determination value at time t2 at the same timing as in "Specific example 2", and the fail-safe process of "Severe" is performed.

"Specific example 8"
Here, as shown in FIG. 14, it is assumed that the heating system 20 fails during execution of the heat generation operation, and the freezing of the reducing agent is not canceled by the time the determination time elapses after the reducing agent freezes. .. In this case, the operation at time t1 is the same as in “Specific Example 7”. However, in this case, after the heating system 20 starts the heat generation operation, at the time t2 when the count value is larger than the second set value and smaller than the first set value, the heating system 20 that was normal until then. Will break down. Therefore, after the time t2, the determination value is set to the second set value. Then, at this time t2, the count value becomes equal to or larger than the determination value, and the "Severe" fail-safe process is performed.

"Specific example 9"
Here, as shown in FIG. 15, it is assumed that the heating system 20 fails during the execution of the heat generation operation and the freezing of the reducing agent is not canceled by the elapse of the determination time after the freezing of the reducing agent. .. In this case, the operation at time t1 is the same as in “Specific Example 7”. However, in this case, after the heating system 20 starts the heat generation operation, at time t2 when the count value is a value smaller than the second set value, the heating system 20 that was normal until then fails.

Therefore, after the time t2, the determination value is set to the second set value. At the time t2, the count value is less than the determination value, so the "Severe" fail-safe process is not executed. After that, by continuing the first counting operation, at time t3 when the count value reaches the determination value, the fail-safe process of "Severe" is performed.

According to this embodiment described above, the following effects can be obtained.
In the present embodiment, the post-processing ECU 11 makes the determination value in the failure period smaller than the determination value in the normal period. According to the present embodiment as described above, similarly to each of the above-described embodiments, the determination time for determining whether or not the fail-safe process can be executed is shortened according to the length of the failure period. The effect of can be obtained.

(Other embodiments)
The present invention is not limited to the embodiments described above and illustrated in the drawings, and can be arbitrarily modified, combined, or expanded without departing from the scope of the invention.
In each of the above embodiments, the engine ECU 1 and the post-processing ECU 11 are provided, and the ECUs are communicably connected. However, as shown in FIG. 16, instead of the engine ECU 1 and the post-processing ECU 11, a post-processing integrated engine ECU 41, which is one electronic control device having both functions of the respective ECUs, may be provided. In this case, as shown in FIG. 17, the post-processing integrated engine ECU 41 includes a fail-safe control section 42 in addition to the freeze detection section 31, the failure determination section 32, and the fail-safe determination section 33 included in the post-processing ECU 11. The fail-safe control section 42 performs fail-safe processing based on the judgment of the fail-safe judgment section 33.

The fail-safe determination unit 33 only needs to be able to measure the freezing duration of the reducing agent using a counter in the FS necessity determination process. For example, the first countdown operation of decrementing each coefficient A may be performed instead of the first countup operation, and the second countdown operation of decrementing each coefficient B may be performed instead of the second countup operation. In that case, the initial value of the counter may be used as the determination value, and each countdown operation may be terminated when the count value reaches zero. Further, in this case, instead of the countdown operation in the third embodiment, a countup operation of incrementing each coefficient C may be performed. In that case, the count-up operation may be terminated when the count value reaches the determination value.

In each of the above-described embodiments, it is shown that whether or not the urea water is frozen is determined based on the detection result of the pressure sensor 19. However, based on the detection result of the temperature sensor provided in the urea water tank 15, it is determined that the urea water is frozen when the temperature detected by the temperature sensor is less than a preset determination value. May be. Further, based on the detection result of the outside air temperature sensor, it may be determined that the urea water has frozen when the temperature detected by the outside air temperature sensor is less than a preset determination value.

2... Internal combustion engine, 11... Post-processing ECU, 20... Heating system, 31... Freezing detection part, 32... Failure judgment part, 33... Fail safe judgment part.

Claims (8)

A freezing detector (31) for detecting freezing of the reducing agent injected into the exhaust gas in order to purify the exhaust gas discharged from the internal combustion engine (2) mounted on the vehicle;
A failure determination unit (32) for determining whether or not the heating system (20) for heating the frozen reducing agent is normal,
A fail-safe determination unit (33) that determines whether to perform a fail-safe process corresponding to the freezing of the reducing agent based on the detection result of the freezing detection unit and the determination result of the failure determination unit;
Equipped with
The fail-safe determination unit is
Performing the fail-safe process when it is determined that the freezing of the reducing agent is not resolved by the time when a predetermined determination time elapses from the time when the reducing agent is frozen,
An electronic control unit that shortens the determination time according to a period in which the failure determination unit determines that the heating system is not normal . The fail-safe determination unit, to claim 1 in which freezing of the reducing agent to start counting from the time it was detected, it is determined that the count value is the determination time when it reaches a predetermined judgment value has elapsed Electronic control device as described. The fail-safe determination unit performs the counting operation in a period in which the failure determination unit determines that the heating system is not normal, and performs the counting operation in a normal period in which the failure determination unit determines that the heating system is normal. electronic control device according to claim 1 or 2 to reduce the judgment time by advancing from counting. The fail-safe determination unit determines the determination value in a period in which the failure determination unit determines that the heating system is not normal, the determination value in a normal period in which the failure determination unit determines that the heating system is normal. electronic control device according to claim 1 or 2 to reduce the determined time by the judgment value smaller value. The electronic control device according to claim 2 , wherein the fail-safe determination unit clears the count value when freezing of the reducing agent is not detected. The fail-safe determination unit returns the count value toward the initial value during a period when the failure determination unit determines that the heating system is normal and during which no freezing of the reducing agent is detected. The electronic control unit according to claim 2 , which performs a reverse counting operation. A freezing detector (31) for detecting freezing of the reducing agent injected into the exhaust gas in order to purify the exhaust gas discharged from the internal combustion engine (2) mounted on the vehicle;
A failure determination unit (32) for determining whether or not the heating system (20) for heating the frozen reducing agent is normal,
A fail-safe determination unit (33) that determines whether to perform a fail-safe process corresponding to the freezing of the reducing agent based on the detection result of the freezing detection unit and the determination result of the failure determination unit;
Equipped with
The fail-safe determination unit is
Performing the fail-safe process when it is determined that the freezing of the reducing agent is not resolved by the time when a predetermined determination time elapses from the time when the reducing agent is frozen,
Starting the counting operation from the time when the reducing agent is frozen, it is determined that the determination time has elapsed when the count value reaches a predetermined determination value,
An electronic control that performs a reverse counting operation for returning the count value toward an initial value during a period in which the failure determination unit determines that the heating system is normal and no freezing of the reducing agent is detected. apparatus. The electronic control device according to any one of claims 1 to 7 , further comprising a fail-safe control unit (42) that performs the fail-safe process based on the determination of the fail-safe determination unit.

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